CoO Nanosheets as Battery-Type Electrode for High-Energy Li-Ion Capacitors: A Sustained Li-Storage Conversion Pathway.

We report the excellent charge storage performance of high-energy Li-ion capacitors (LIC) fabricated from the mesoporous CoO nanosheets as the conversion-type battery component and Jack fruit () derived activated carbon as a supercapacitor electrode, especially at high temperatures (50 and 40 °C). Prior to the fabrication, the electrochemical prelithiation strategy was applied to CoO to alleviate the irreversibility and enrich the Li-ions for electrochemical reactions (Co + LiO). The LIC delivered a maximum energy density of ∼118 Wh kg at a high temperature of 50 °C. The significant difference is observed at a high rate of 2.6 kW kg at 50 °C with excellent cycle stability up to 3000 cycles, with a retention of ∼87% compared with the LIC cycled at room temperature (∼74%). The magnificent electrochemical performance clearly demonstrates that the mesoporous structure and residual carbon synergistically facilitated the Li/electron transport and hinder undesirable side reactions with electrolytes to realize high-energy density at high temperatures.